Generally, the widely-used peripheral input device of a computer system includes for example a mouse, a keyboard, a trackball, or the like. Via the keyboard, characters or symbols can be directly inputted to the computer system. As a consequence, most users and most manufacturers of input devices pay much attention to the development of the keyboards. As known, a keyboard with scissors-type connecting elements is one of the widely-used keyboards.
A keyboard with scissors-type connecting elements will be illustrated as follows. For succinctness, only one key structure is shown. FIG. 1 is a schematic side cross-sectional view illustrating a key structure of a conventional keyboard. As shown in FIG. 1, the conventional key structure 1 comprises a keycap 11, a scissors-type connecting element 12, a rubbery elastomer 13, a membrane switch circuit member 14 and a base plate 15. The keycap 11, the scissors-type connecting element 12, the rubbery elastomer 13 and the membrane switch circuit member 14 are supported by the base plate 15. The scissors-type connecting element 12 is used for connecting the base plate 15 and the keycap 11.
The membrane switch circuit member 14 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated. The rubbery elastomer 13 is disposed on the membrane switch circuit member 14. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The scissors-type connecting element 12 is arranged between the base plate 15 and the keycap 11, and the base plate 15 and the keycap 11 are connected with each other through the scissors-type connecting element 12. The scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the base plate 15. The rubbery elastomer 13 is enclosed by the scissors-type connecting element 12. Moreover, the first frame 121 comprises a first keycap post 1211 and a first base plate post 1212. The first frame 121 is connected with the keycap 11 through the first keycap post 1211. The first frame 121 is connected with the base plate 15 through the first base plate post 1212. The second frame 122 is combined with the first frame 121. A first end of the second frame 122 is connected with the base plate 15. A second end of the second frame 122 is connected with the keycap 11. Moreover, the second frame 122 comprises a second keycap post 1221 and a second base plate post 1222. The second frame 122 is connected with the keycap 11 through the second keycap post 1221. The second frame 122 is connected with the base plate 15 through the second base plate post 1222.
The operations of the conventional key structure 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 1 again. While the keycap 11 is depressed, the keycap 11 is moved downwardly to push the scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the base plate 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. In response to the elastic restoring force, the keycap 11 is returned to its original position where it is not depressed.
Recently, the general trends of designing electronic devices and their peripheral devices are toward slimness, light weightiness an easy portability. Consequently, keyboard devices and other peripheral devices need to meet the requirements of slimness. For achieving this purpose, the manufacturers make efforts in minimizing the thickness of the keyboard. Conventionally, two approaches are used to reduce the thickness of the keyboard. In a first approach, the thicknesses of some components or all components of the key structure are decreased. In a second approach, the movable distance of the keycap (also referred as a travelling distance) is shortened. However, these approaches still have some drawbacks. In case that the first approach is adopted, the structural strength of the key structure is impaired, and thus the key structure is easily damaged. In case that the second approach is adopted, the tactile feel of depressing the key structure is deteriorated. In other words, it is difficult to reduce the thickness of the keyboard while obtaining the desired tactile feel.
Therefore, there is a need of providing a key structure with reduced thickness and enhanced tactile feel.